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  <title>如果对象属于该类或该类是此对象的父类则返回 TRUE</title>
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 <body class="docs"><div id="layout">
  <div id="layout-content"><div id="function.is-a" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">is_a</h1>
  <p class="verinfo">(PHP 4 &gt;= 4.2.0, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">is_a</span> &mdash; <span class="dc-title">如果对象属于该类或该类是此对象的父类则返回 <strong><code>TRUE</code></strong></span></p>

 </div>
 <div class="refsect1 description" id="refsect1-function.is-a-description">
    <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>is_a</strong></span>
    ( <span class="methodparam"><span class="type">object</span> <code class="parameter">$object</code></span>
   , <span class="methodparam"><span class="type">string</span> <code class="parameter">$class_name</code></span>
   [, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$allow_string</code><span class="initializer"> = <strong><code>FALSE</code></strong></span></span>
  ] ) : <span class="type">bool</span></div>

  <p class="para rdfs-comment">
   如果 <code class="parameter">object</code> 是该类或该类是此对象的父类。
  </p>
 </div>

 <div class="refsect1 parameters" id="refsect1-function.is-a-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<code class="parameter">object</code></dt>

     <dd>

      <p class="para">
       The tested object
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">class_name</code></dt>

     <dd>

      <p class="para">
       The class name
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">allow_string</code></dt>

     <dd>

      <p class="para">
       If this parameter set to <strong><code>FALSE</code></strong>, string class name as <code class="parameter">object</code>
       is not allowed. This also prevents from calling autoloader if the class doesn&#039;t exist.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 
 <div class="refsect1 returnvalues" id="refsect1-function.is-a-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns <strong><code>TRUE</code></strong> if the object is of this class or has this class as one of
   its parents, <strong><code>FALSE</code></strong> otherwise.
  </p>
 </div>

 <div class="refsect1 changelog" id="refsect1-function.is-a-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>5.3.9</td>
       <td>
        Added <code class="parameter">allow_string</code> parameter
       </td>
      </tr>

      <tr>
       <td>5.3.0</td>
       <td>
        This function is no longer deprecated, and will therefore 
        no longer throw <strong><code>E_STRICT</code></strong> warnings.
       </td>
      </tr>

      <tr>
       <td>5.0.0</td>
       <td>
        This function became deprecated in favour of the 
        <a href="language.operators.type.html" class="link">instanceof</a> 
        operator. Calling this function will result in an 
        <strong><code>E_STRICT</code></strong> warning.
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>

 <div class="refsect1 examples" id="refsect1-function.is-a-examples">
  <h3 class="title">范例</h3>
  <p class="para">
    <div class="example" id="example-6147">
      <p><strong>Example #1 <span class="function"><strong>is_a()</strong></span> 例子</strong></p>
      <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;define&nbsp;a&nbsp;class<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">WidgetFactory<br /></span><span style="color: #007700">{<br />&nbsp;&nbsp;var&nbsp;</span><span style="color: #0000BB">$oink&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'moo'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;create&nbsp;a&nbsp;new&nbsp;object<br /></span><span style="color: #0000BB">$WF&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">WidgetFactory</span><span style="color: #007700">();<br /><br />if&nbsp;(</span><span style="color: #0000BB">is_a</span><span style="color: #007700">(</span><span style="color: #0000BB">$WF</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'WidgetFactory'</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"yes,&nbsp;\$WF&nbsp;is&nbsp;still&nbsp;a&nbsp;WidgetFactory\n"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
      </div>

    </div>
   <div class="example" id="example-6148">
    <p><strong>Example #2 在 PHP 5 中使用 <em class="emphasis">instanceof</em> 运算符</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$WF&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">WidgetFactory</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'Yes,&nbsp;$WF&nbsp;is&nbsp;a&nbsp;WidgetFactory'</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

   </div>
  </p>
 </div>

 <div class="refsect1 seealso" id="refsect1-function.is-a-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="get_class.html" class="function" rel="rdfs-seeAlso">get_class()</a> - 返回对象的类名</span></li>
    <li class="member"><span class="function"><a href="get_parent_class.html" class="function" rel="rdfs-seeAlso">get_parent_class()</a> - 返回对象或类的父类名</span></li>
    <li class="member"><span class="function"><a href="is_subclass_of.html" class="function" rel="rdfs-seeAlso">is_subclass_of()</a> - 如果此对象是该类的子类，则返回 TRUE</span></li>
   </ul>
  </p>
 </div>

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